It is often necessary to detect the presence and identity of a pollutant, contaminant or toxic species remotely, quickly and accurately, such as in atmospheric or effluent monitoring and control. Fast, positive detection is also of critical importance in defense against biological and chemical attack. Fast identification not only provides the time to don protective clothing, but also to select the proper antidote. Positive identification is important because the wrong antidote can be as lethal as the chemical species. Also, protective clothing can significantly degrade the effectiveness of combat personnel so false alarms should be minimized.
Present detection techniques suffer from a number of shortcomings. Some operate at wavelengths where the chemical signatures are not easily distinguished; some sense reflected radiation of the same wavelength as the laser and are subject to interference from natural atmospheric or aerosol scattering at the laser wavelength. Others cannot operate remotely or can sense only gases or only liquids or only aerosols, which makes them less than optimum for portable detection on site or on the battlefield.